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<div class="title">ripple::packed_spinlock&lt; T &gt; Class Template Reference</div> </div>
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<p>Classes to handle arrays of spinlocks packed into a single atomic integer:
<a href="classripple_1_1packed__spinlock.html#details">More...</a></p>
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Public Member Functions</h2></td></tr>
<tr class="memitem:a9b50344098f14a88e3cf3bf75f9eca45"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a9b50344098f14a88e3cf3bf75f9eca45">packed_spinlock</a> (<a class="el" href="classripple_1_1packed__spinlock.html">packed_spinlock</a> const &amp;)=delete</td></tr>
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<tr class="memitem:a02dd3a51a505ba7bf9e913314549773d"><td class="memItemLeft" align="right" valign="top"><a class="el" href="classripple_1_1packed__spinlock.html">packed_spinlock</a> &amp;&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a02dd3a51a505ba7bf9e913314549773d">operator=</a> (<a class="el" href="classripple_1_1packed__spinlock.html">packed_spinlock</a> const &amp;)=delete</td></tr>
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<tr class="memitem:a6b795f06719bc2d90ed4f6a6007fb5fe"><td class="memItemLeft" align="right" valign="top">&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a6b795f06719bc2d90ed4f6a6007fb5fe">packed_spinlock</a> (<a class="elRef" href="http://en.cppreference.com/w/cpp/atomic/atomic.html">std::atomic</a>&lt; T &gt; &amp;<a class="el" href="classripple_1_1packed__spinlock.html#a8d885a8f4e6fc078869345131e76be63">lock</a>, int index)</td></tr>
<tr class="memdesc:a6b795f06719bc2d90ed4f6a6007fb5fe"><td class="mdescLeft">&#160;</td><td class="mdescRight">A single spinlock packed inside the specified atomic. <a href="classripple_1_1packed__spinlock.html#a6b795f06719bc2d90ed4f6a6007fb5fe">More...</a><br /></td></tr>
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<tr class="memitem:ad544b64b85215e6adcf96a37f7b14503"><td class="memItemLeft" align="right" valign="top">bool&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#ad544b64b85215e6adcf96a37f7b14503">try_lock</a> ()</td></tr>
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<tr class="memitem:a8d885a8f4e6fc078869345131e76be63"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a8d885a8f4e6fc078869345131e76be63">lock</a> ()</td></tr>
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<tr class="memitem:a54ab44d231a3a27eda752596b3f69e11"><td class="memItemLeft" align="right" valign="top">void&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a54ab44d231a3a27eda752596b3f69e11">unlock</a> ()</td></tr>
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Private Attributes</h2></td></tr>
<tr class="memitem:a1f775dfb309d7f877b5075c05a29d857"><td class="memItemLeft" align="right" valign="top"><a class="elRef" href="http://en.cppreference.com/w/cpp/atomic/atomic.html">std::atomic</a>&lt; T &gt; &amp;&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#a1f775dfb309d7f877b5075c05a29d857">bits_</a></td></tr>
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<tr class="memitem:add775fd5d7375664092b675670d5ca6b"><td class="memItemLeft" align="right" valign="top">const T&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="classripple_1_1packed__spinlock.html#add775fd5d7375664092b675670d5ca6b">mask_</a></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><h3>template&lt;class T&gt;<br />
class ripple::packed_spinlock&lt; T &gt;</h3>
<p>Classes to handle arrays of spinlocks packed into a single atomic integer: </p>
<p>Packed spinlocks allow for tremendously space-efficient lock-sharding but they come at a cost.</p>
<p>First, the implementation is necessarily low-level and uses advanced features like memory ordering and highly platform-specific tricks to maximize performance. This imposes a significant and ongoing cost to developers.</p>
<p>Second, and perhaps most important, is that the packing of multiple locks into a single integer which, albeit space-efficient, also has performance implications stemming from data dependencies, increased cache-coherency traffic between processors and heavier loads on the processor's load/store units.</p>
<p>To be sure, these locks can have advantages but they are definitely not general purpose locks and should not be thought of or used that way. The use cases for them are likely few and far between; without a compelling reason to use them, backed by profiling data, it might be best to use one of the standard locking primitives instead. Note that in most common platforms, <code><a class="elRef" href="http://en.cppreference.com/w/cpp/thread/mutex.html" title="STL class.">std::mutex</a></code> is so heavily optimized that it can, usually, outperform spinlocks.</p>
<dl class="tparams"><dt>Template Parameters</dt><dd>
<table class="tparams">
<tr><td class="paramname">T</td><td>An unsigned integral type (e.g. <a class="elRef" href="http://en.cppreference.com/w/cpp/types/integer.html">std::uint16_t</a>) A class that grabs a single packed spinlock from an atomic integer.</td></tr>
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</dd>
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<p>This class meets the requirements of Lockable: <a href="https://en.cppreference.com/w/cpp/named_req/Lockable">https://en.cppreference.com/w/cpp/named_req/Lockable</a> </p>
<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00089">89</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
</div><h2 class="groupheader">Constructor &amp; Destructor Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a9b50344098f14a88e3cf3bf75f9eca45">&#9670;&nbsp;</a></span>packed_spinlock() <span class="overload">[1/2]</span></h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a6b795f06719bc2d90ed4f6a6007fb5fe">&#9670;&nbsp;</a></span>packed_spinlock() <span class="overload">[2/2]</span></h2>
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<td class="paramtype"><a class="elRef" href="http://en.cppreference.com/w/cpp/atomic/atomic.html">std::atomic</a>&lt; T &gt; &amp;&#160;</td>
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<p>A single spinlock packed inside the specified atomic. </p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">lock</td><td>The atomic integer inside which the spinlock is packed. </td></tr>
<tr><td class="paramname">index</td><td>The index of the spinlock this object acquires.</td></tr>
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</dd>
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<dl class="section note"><dt>Note</dt><dd>For performance reasons, you should strive to have <code>lock</code> be on a cacheline by itself. </dd></dl>
<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00117">117</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<h2 class="groupheader">Member Function Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a02dd3a51a505ba7bf9e913314549773d">&#9670;&nbsp;</a></span>operator=()</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#ad544b64b85215e6adcf96a37f7b14503">&#9670;&nbsp;</a></span>try_lock()</h2>
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<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00124">124</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<h2 class="memtitle"><span class="permalink"><a href="#a8d885a8f4e6fc078869345131e76be63">&#9670;&nbsp;</a></span>lock()</h2>
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<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00130">130</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00144">144</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<h2 class="groupheader">Member Data Documentation</h2>
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<h2 class="memtitle"><span class="permalink"><a href="#a1f775dfb309d7f877b5075c05a29d857">&#9670;&nbsp;</a></span>bits_</h2>
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<td class="memname"><a class="elRef" href="http://en.cppreference.com/w/cpp/atomic/atomic.html">std::atomic</a>&lt;T&gt;&amp; <a class="el" href="classripple_1_1packed__spinlock.html">ripple::packed_spinlock</a>&lt; T &gt;::bits_</td>
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<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00092">92</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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<p class="definition">Definition at line <a class="el" href="spinlock_8h_source.html#l00102">102</a> of file <a class="el" href="spinlock_8h_source.html">spinlock.h</a>.</p>
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